"A number of rioters and vandals had been arrested for taking part in illegal rallies and gatherings, blocking roads and endangering people's lives by attacking them with petrol bombs, iron rods and stones," the Information Affairs Authority said in a statement, citing Maj-Gen Tariq Al Hassan.

A local journalist told the BBC the demonstrators in Old Manama were shouting "Down, down, F1" and demanding the release of Abdulhadi al-Khawaja, an activist who has been on hunger strike in prison for more than two months.

Mr Khawaja is now said to be refusing everything except water.

Another protest has been called for 16:00 local time (14:00 GMT) outside the Bahrain International Circuit. Correspondents say riot police will have to show restraint with the international media so close at hand.

The BBC's Rupert Wingfield-Hayes in Manama says the protesters are determined to use the race to draw attention to their campaign, while the government is determined to stop them.

Bahrain's ruling royal family are being pressured to improve human rights and make reforms by the majority Shia population, who accuse the minority ruling Sunnis of discrimination.